1. Field of the Invention
The present invention relates to an energy usage display unit for displaying energy usage such as usage of gas or water service for a water heater or usage of electricity at housing where the water heater is set.
2. Description of the Related Art
Conventionally, there is a known water heater which can display usage of gas or water used for a water heater (Japanese Patent No. 3061215). As shown in a block diagram in FIG. 6, as a configuration for displaying usage of gas and the like, the water heater includes gas amount detecting means 631, water amount detecting means 641, gas amount integrating means 674, water amount integrating means 675, periodic integrating and managing means 673, memory means 677, display means 676, display switching means 678, integrating period setting means 671, clock means 672 and the like.
The gas amount integrating means 674 adds up a gas amount used in a water heater main body (not shown) detected by the gas amount detecting means 631. The water amount integrating means 675 adds up a water amount used in the water heater main body detected by the water amount detecting means 641. The integrating period setting means 671 sets a reference day of integration, and inputs a reference day data 671a to the periodic integrating and managing means 673. The clock means 672 has a calendar function, and supplies clock data 672a such as month, day, hour, minute to the periodic integrating and managing means 673.
The periodic integrating and managing means 673 compares the reference day data 671a with the clock data 672a, reads integration results 674a, 675a of the gas amount integrating means 674 and the water amount integrating means 675 every integration period, stores the integration results 674a, 675a in the memory means 677 in association with the integration period, generates reset signals 673a, 673b to clear the integration values of the gas amount integrating means 674 and the water amount integrating means 675, and restarts the integration from zero.
The water heater adds up the gas amount and an water amount used in the water heater main body by means of the gas amount integrating means 674 and the water amount integrating means 675 (hereinafter generally referred to “integrating means 674, 675”,) over the integration period which is set by the integrating period setting means 671, and displays the integration results 674a, 675a using the display means 676. In a case where it is requested to display a past usage by designating year and month from the display switching means 678, corresponding data is read out from the memory means 677 and is displayed on the display means 676.
According to the conventional water heater, if the periodic integrating and managing means 673 outputs the reset signals 673a, 673b based on the integration period which is set by the integrating period setting means 671, the integrating means 674, 675 adds up usage of gas and water service in accordance with the integration period, and the display means 676 shows the integration results 674a, 675a in accordance with the integration period. Therefore, in order to change the period unit (month unit or the like) of usage which is displayed on the display means 676, it is necessary to again set the integration period by the integrating period setting means 671, change output timing of the reset signals 673a, 673b of the periodic integrating and managing means 673, and change the integration periods of the integrating means 674, 675.
In this case, if the integration period is changed, the periodic integrating and managing means 673 outputs the reset signals 673a, 673b to the integrating means 674, 675, and, clears the integration values of the integrating means 674, 675, and restarts the integration. Therefore, the current usage which is added up by the integrating means 674, 675 is cleared and the usage can not be displayed. Further, the data stored in the memory means 677 has a different integration period from that before the integration period is changed and thus, the past usage can not be displayed either.
The integration period in the periodic integrating and managing means 673 is obtained by the reference day data 671a of the integrating period setting means 671 and the time-counting data 672a of the clock means 672. Therefore, time of the clock means 672 is changed, the integration period is reduced or increased by the corresponding time before or after the change and thus, the integration period of the periodic integrating and managing means 673 is changed. Therefore, the periodic integrating and managing means 673 outputs the reset signals 673a, 673b to the integrating means 674, 675 by the change of the integration period caused by the change in time, and the periodic integrating and managing means 673 clears the integration values of the integrating means 674, 675 and restarts the integration. Thus, in this case also, the current usage which is added up by the integrating means 674 and 675 is cleared and the current usage can not be displayed.